1. Field of the Invention
This invention relates generally to the field of handlers for feeding integrated circuit or semiconductor devices to a tester for testing and evaluating the integrated circuit devices. More particularly, the invention relates to a handler apparatus for heating or cooling the integrated circuit or semiconductor devices to temperature conditions under which the devices will operate for testing.
2. Description of the Art
Various types of integrated circuit devices having evolved since the development of the semiconductor. Such devices have innumerable applications in industry and commerce. In many of these applications, it is essential that these devices be accurate to a defined minimum percentage of accuracy. Thus, it is necessary to test the integrated circuit devices to determine whether or not they are operable and to what degree. Various high speed testing devices have been developed to measure to the quality of such integrated circuit devices. Typically, such testers can perform testing upon units at very high rates of speed. Accordingly, it has been necessary to provide handling equipment capable of rapidly feeding integrated circuit devices to a test site.
Depending on the type of the device and the application to which it is to be put, the device will be subjected to different environmental operating temperatures. For example, in one application, the semiconductor device which is being tested will ultimately function in an environment with a temperature significantly higher than ambient room temperature. Alternatively, a semiconductor device may be required to operate throughout a wide range of temperature and may require testing at different temperature extremes.
It is follows that a particularly important feature of any integrated circuit handler is that it brings the integrated circuit or semiconductor devices being handled to the temperatures at which they will ultimately operate and maintains tight control of the temperature. A variety of methods are known in the prior art for thermally conditioning semiconductor devices prior to being tested. For example, it is known to provide a soak chamber adjacent the tester so that as the semiconductor devices are transported through the soak chamber to the tester, the soak chamber brings the temperature of the semiconductor devices to the specified temperature for testing. In heating the semiconductor devices in the soak chamber, typically heaters are utilized to heat the air within the soak chamber. The heating elements may be located at the intake of a blower so that the heated air is then circulated within the soak chamber to heat the semiconductor devices. For example, U.S. Pat. No. 4,462,796 to Amundson et al. discloses an air heating system for use in heating integrated circuit chip carriers prior to the chips being tested by an electronic tester. If it is desired to cool the semiconductor devices to be tested, a typical soak chamber may include a separate cooling system such as introducing a gas of the desired temperature into the chamber to surround the semiconductor devices as they pass through the chamber. For example, a liquid nitrogen tank may be connected to a solenoid valve for introducing nitrogen gas into the soak chamber to cool the devices.
One problem with such methods of heating or cooling the semiconductor devices is the time required for changing the temperature of the soak chamber when the devices are to be tested at different temperatures. For example, to change a typical handler apparatus from testing semiconductor devices at a higher temperature such as +125 degrees Celsius to test devices at a lower temperature such as -25 degrees Celsius, it may take 30 minutes or more for the soak chamber to cool down to the desired temperature to thermally condition the semiconductor devices. Another problem is that the soak chamber constitutes an enclosed area and the system provides for the heating or cooling of the entire soak chamber including the air and the walls and base of the soak chamber as well as the semiconductor devices to be thermally conditioned. This results in wasted energy in heating or cooling of the semiconductor devices. Another problem with such soak chambers is that it is difficult to maintain the temperature of the semiconductor devices at a specific temperature. For example, there may be variations within the soak chamber so that some of the semiconductor devices differ in temperature from other devices within the chamber so that all the semiconductor devices are not tested at precisely the same temperature. Also, the enclosed nature of the soak chamber limits access to the semiconductor devices as they are transported to the tester.
Another example of a method for thermally conditioning semiconductor devices includes heating a rail on which the semiconductor devices are placed. For example, U.S. Pat. No. 4,579,527 to Wedel discloses an apparatus in which integrated circuits are transported down a track and rail in which the track and rail are heated in order to impart thermal energy to the integrated circuit devices passing down the tracks. A significant problem with such an apparatus is that it is only able to heat the integrated circuit devices and does not provide thermal conditioning for integrated circuits at lower temperatures.
What is needed is an apparatus for thermally conditioning semiconductor devices in which the semiconductor devices are quickly brought to a specified temperature and maintained at that temperature with minimum temperature fluctuation. What is further needed is an apparatus which is able to thermally condition semiconductor devices over a large range of temperatures and is able to change temperatures within a short time frame.